Project Summary Although childhood obesity is a national health problem reaching epidemic proportions, Hispanic children are nearly twice as likely as non-Hispanic white children to be obese, and Mexican Americans have higher risk of obesity than other Hispanic subgroups. Weight-associated health problems are also increasing at alarming rates. If contemporary obesity prevalence rates persist, ?the current generation of children will be the first generation in US history to be sicker and die earlier than their parents? (Robert Wood Johnson Foundation, 2012). Because the challenges of intervention are multiplied after a child has already reached obesity status, it is imperative to understand the processes of developing risk in the earliest years of life. The identification of risk and resiliency predictors of the development of obesity during critical formative years of childhood will provide specific targets amenable to preventive public health interventions. We propose to capitalize on longitudinal data collected by an NIMH and NICHD-funded study of very low income Mexican American mothers and infants (Las Madres Nuevas) that assesses a multitude of cultural and environmental risk and protective factors from the prenatal period through six years of age. We propose to leverage this existing longitudinal dataset, and collect physical health and markers of cardiometabolic risk at ages 7.5 and 9. In combination, we will: 1) Use advanced statistical procedures to chart trajectories of weight gain using objective measures of weight and growth measured at 13 time points from birth through age 9; 2) Identify critical periods from birth to age 9 at which children diverge from healthy weight gain trajectories; 3) Evaluate early life biological susceptibility as a moderator of the impact of environmental influences on child weight gain trajectories and obesity; 4) Evaluate the consequences of cultural, economic, maternal and child factors, and weight gain trajectories for emerging physical health and cardiometabolic risk. The proposed longitudinal study, with data drawn from biological measures, anthropometric measures, parent report, medical records, and observational sessions, is ideally situated to answer key questions related to weight disparities among low- income MA children, and delineate mechanistic pathways in the emergence of MA child obesity. Our scientific approach emphasizes the cultural embeddedness of obesity development, with the view that the reduction of child obesity disparities can best be accomplished by understanding sociocultural and economic forces that shape eating behavior and weight gain. This project holds great potential to address central questions about early life contributors to weight gain and obesity risk in a high risk ethnic group, and enhance opportunities for prevention of obesity and associated health problems.